<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>测试全局变量</title>
</head>
<body>
	<script>
		var test = function(a) {
			a = a || 5;
			// b = a || 5;
			console.log(a);
		};
		test();
		console.log(a);
		// console.log(b);
	</script>
</body>
</html>